1. Field of the Invention
This invention relates to vehicle wheels/rims of the type to which a separable tire is mounted and, more particularly, to a method of processing a vehicle wheel/rim preform to form surfaces thereon to seat inboard and outboard beads on a tire. The invention is further direction to an apparatus for practicing the method.
2. Background Art
Myriad wheel/rim constructions have evolved over the decades to accept inflatable tires on all types of vehicles, from recreational to commercial applications. The basic wheel/rim construction consists of a centersection/spider, through which the wheel/rim is mounted to a vehicle, and an annular wall, which cooperates with the tire. The annular wall has inboard and outboard flanges, spaced axially with respect to the rotational axis for the wheel/rim, which respectively seat inboard and outboard beads on a tire.
Heretofore, the annular wall has been manufactured either with one piece or using a multi-part construction. With a multi-part construction, the wheel/rim “halves” are separately machined and mechanically joined to produce a unitary structure. This multi-part construction represents an expedient in terms of the manufacturing process but creates a challenge to the manufacturer in terms of maintaining dimensional, alignment, and balance tolerances. The automotive industry is becoming increasingly demanding that the wheel/rim be precisely machined so that there are no appreciable irregularities or defects that will cause vibrations, particularly at high operating speeds.
Whereas in the past, most wheels/rims in the automotive industry were designed to be used in conjunction with decorative hubcaps, the recent trend has been to expose the centersection/spider. This has prompted vehicle manufacturers to place even stricter demands on wheel/rim manufacturers, not only in terms of dimensions and balance, but also in terms of appearance.
Meeting the industry demands offers a particular challenge to wheel/rim manufacturers with respect to the wheel/rim designs wherein a single piece is utilized to form the annular wall between the inboard and outboard flanges. In a typical manufacturing process, the vehicle wheel/rim preform is cast or otherwise formed. The preform is clamped upon a lathe spindle and rotated to allow machining, including on the seating surface on the annular wall, to end specifications. In carrying out this machining, it is important that the preform be positively maintained upon a spindle chuck so that the annular wall can be precisely formed based on certain datum locations. This requires that the preform be clamped in such a manner that it does not shift or deform and is not prone to having induced harmonic vibrations that may adversely alter the machining process.
To avoid these latter conditions, it is known to clamp the preform to the chuck in the region of one of the flanges at a plurality of angularly spaced locations, as shown in U.S. Pat. No. 5,820,137. To effect the required clamping rigidity, a clamping structure is typically utilized at a wheel/rim flange which blocks machining of the wheel/rim in the vicinity of the flange. Generally, in the past, this has necessitated a two step clamping and machining operation. That is, after clamping one of the inboard and outboard flanges and machining accessible regions on the wheel/rim, the wheel/rim is axially inverted and the other of the inboard and outboard regions is exposed to allow machining of the previously clamped portions.
For this machining operation to be effective, the preform must be precisely axially aligned in the reversed clamping orientation. Even slight misalignments may result in an imbalanced structure and/or a detectable step at the location where the machining processes meet. Due to the increasing sensitivity of the automotive industry to even slight imperfections, this process may be impractical to carry out in an economical manner.
One attempted solution to this problem has been to machine between the inboard and outboard flanges with the wheel/rim maintained in a single clamped position on the spindle chuck, as described in U.S. Pat. No. 6,126,174. In U.S. Pat. No. 6,126,174, the preform is required to be constructed with a flange extension which facilitates clamping and ultimately must be removed in a separate processing step. Consequently, additional material must be added to the preform and an additional manufacturing step is required to remove the extension and finish the flange at which the extension is removed to complete the wheel/rim. Additional steps are thus required to machine the wheel/rim. These additional steps add time to the manufacturing process and thereby potentially adversely affect profitability. Further, the material defining the extension must be appropriately handled and disposed of, representing another inconvenience and expense.